Strain Relaxation of Zn Quantum Dots Grown on Si (111) by Thermal Expansion
Li-Chi Kao1*, Bo-Jia Huang1, Sanjaya Brahma1, Yu-En Jeng1, Shang-Jui Chiu2, Ching-Shun Ku2, Kuang-Yao Lo1
11. Department of Physics, National Cheng Kung University, Tainan, Taiwan
22. National Synchrotron Radiation Research Center, Hsinchu, Taiwan
* presenting author:Li- Chi Kao,
Zn quantum dots constrained on Si (111) provide ideal ohmic or Schottky contacts with less electronic scattering. It is a significant issue to research thermal relaxation of metallic nano-contacts for further application of nano-devices. Particularly, metallic nano-contact constrainedly grown on the semiconductor components as contacts or interconnects. Thermal relaxation will be induced and reduce the conductivity due to the large discrepancy of the thermal expansion coefficient between the interface of metal/semiconductor. It is important to study structural changes of metallic nanoparticles grown on the substrate and their interface after thermal treatments. We used strategic RF magnetron sputtering to fabricate Zn quantum dots coherently grown on the Si (111) substrate and analyzed constrained Zn quantum dots by reflective second harmonic generation (RSHG). Fully constrained Zn dots contributed net 3m symmetrical dipole to RSHG pattern since ZnO/Zn dot arrays provide non-cancelled dipole contribution from a huge assembly of ~109 constrained ZnO/Zn dots. Synchrotron X-ray diffraction (XRD) patterns could confirm RSHG result and give the evolution of all possible crystal orientations due to thermal treatment. Besides, we utilized the field emission - scanning electron microscope (FE-SEM) to observe the micrographs and size distributions. The process of thermal annealing cause larger Zn dots to relax from Si(111) and to induce the further constrain for smaller. The merit of this work is to reveal the constrain degree for Zn dots system with different size distribution. As a result, we further solve the key problem of relaxation of metallic dots grown on semiconductor as the reference of nano-device in the future.

Keywords: Zn dots, Second harmonic generation, Thermal relaxation